Well, I have to say that I think that your changing X's profile such leaves you looking perhaps not as big, and not carrying the dignity and class that you will want to remember some time from now. When you are feeling better than you are now.
I wanted to post on my wall: X is a cheating, cowardly, liar! and then post the rest of the gory details.
Friends convinced me that the best thing to do was send FB email and give the news that way. More discreet. Better taste. Etc.
So I did, and I feel good about that. I did respond to some of my friends' notes with the gory details, and invited them to pass them on as they wanted to. So--I am not perfect!! I want the world to know what a terrible person X is!
That's my .02 cents--and I would also suggest just staying the heck away from your X's FB page. Unfriend her, and her friends. FB is just really too evil an invention. Don't torture yourself by looking at her page.
You always want to look like the better person, no matter what it takes.